Fluid streams including xe2x80x9cdrinkingxe2x80x9d water, as well as effluents, originating from various chemical processes at production sites can contain mixtures of chlorate and bromate. This creates an environmental problem, since it has been demonstrated that bromate has carcinogenic properties and that chlorate is highly toxic to bladder wrack. Chlorate and bromate can be removed from industrial effluents by chemical reduction, but this is expensive and introduces new chemicals into the environment.
Bromate is formed as a by-product of the ozonation of bromide-containing waters. Ozonation is one of the promising alternatives to chlorination, since it avoids the formation of hazardous adsorbable organic halogen (AOX) by-products. The level of bromate found in ozonated drinking water depends on many factors, including the natural level of bromide in the source water and the ozone dose. Typical concentrations of bromate found in ozonated water are in the range of 3-50 xcexcg/l The World Health Organisation (WHO) has proposed a level of 0.5 xcexcg/l bromate for drinking water in the last revision of their guidelines (WHO, 1993), but based on the present analytical feasibilities a provisional level of 25 xcexcg/l was recommended. Because these concentrations may be exceeded by the common ozonation practice, efficient methods to decrease the level of bromate in ozonated water are needed.
It is an object of the present invention to provide an improved process for dealing with this problem.
The present invention provides a process for the removal of undesirable bromine salts from fluid streams, especially waste and/or drinking water streams, comprising the step of exposing the fluid stream to a micro-organism which biochemically aids the reduction of undesirable bromine salts, wherein the micro-organism can transform an energy source in the fluid stream into an electron donor, with the bromine salts functioning as electron acceptors to subsequently accept electrons from the donor thus being reduced.